GB2336481A - Protection of electric heating element - Google Patents
Protection of electric heating element Download PDFInfo
- Publication number
- GB2336481A GB2336481A GB9807385A GB9807385A GB2336481A GB 2336481 A GB2336481 A GB 2336481A GB 9807385 A GB9807385 A GB 9807385A GB 9807385 A GB9807385 A GB 9807385A GB 2336481 A GB2336481 A GB 2336481A
- Authority
- GB
- United Kingdom
- Prior art keywords
- thick film
- heating element
- ptc
- ptc material
- resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000005485 electric heating Methods 0.000 title description 4
- 238000010438 heat treatment Methods 0.000 claims abstract description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims description 24
- 238000009835 boiling Methods 0.000 claims description 2
- 239000011521 glass Substances 0.000 claims description 2
- 230000007704 transition Effects 0.000 claims description 2
- 238000010009 beating Methods 0.000 claims 1
- 230000001747 exhibiting effect Effects 0.000 claims 1
- 230000009477 glass transition Effects 0.000 claims 1
- 230000004048 modification Effects 0.000 claims 1
- 238000012986 modification Methods 0.000 claims 1
- 238000013021 overheating Methods 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003670 easy-to-clean Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000000246 remedial effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0227—Applications
- H05B1/0252—Domestic applications
- H05B1/0258—For cooking
- H05B1/0269—For heating of fluids
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
- H02H5/042—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature using temperature dependent resistors
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
- H05B3/34—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs
- H05B3/36—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs heating conductor embedded in insulating material
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/013—Heaters using resistive films or coatings
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/017—Manufacturing methods or apparatus for heaters
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/02—Heaters using heating elements having a positive temperature coefficient
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/021—Heaters specially adapted for heating liquids
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Control Of Resistance Heating (AREA)
Abstract
A thick film heating element 1 in a kettle or other water heating apparatus is associated with a PTC resistor 5. When a main switch 7 is on, and a switch 6 is briefly closed, current flows through a coil 4, closing contacts 3 and energising the heater 1. If the element 1 overheats, resistor 5 reduces the current in coil 4, so that contacts 3 open and the heater 1 is disconnected from the main supply. Alternatively, the relay may be arranged to cycle on and off if overheating occurs (Figure 2, not shown).
Description
2336481 1 IMPROVEMENTS RELATING TO CONTROL OF ELECTRIC HEATING ELEMENTS
Field of the Invention:
This invention concerns improvements relating to the control of electric heatine, elements, particularly though not exclusively electric heating elements 0 for water boiling vessels such as kettles, jugs, pots, pans, laboratory equipment etc., and particularly though not exclusively electrical heating elements of the so-called thick film type comprising a substrate having a resistance heating 0 C1 layer or track formed thereon with suitable insulation layers overlying and/or underlying the resistance heating layer or track.
Back2round of the Invention:
Thick film electric heating elements are considered to be aesthetically more attractive than conventional immersion heating elements of the type comprising a resistance heating wire packed with insulation material within an elonaate metal sheath on account of the fact that, with a thick film heatina element forming for example the base of a vessel, there is no intrusion of the element into the body volume of the vessel which, inter alia, makes the vessel more easy to clean. Conventional sheathed immersion heating elements, on the other hand, necessarily intrude into the vessel interior and, particularly in hard ide a f water areas, can provi ocus for unsightly scale deposits.
4 resistance, or of a plurality of discrete PTC resistances suitably distributed over the surface area of the heating element, or around its periphery, and connected electrically in series with each other. It could be comprised in or as a track of the heatinu element, and formed for example by printing a suitable PTC thick Z= film paste onto a dielectric layer of the heating element. It could be formed as a continuous track or as a plurality of short tracks joined by a printed conductor. Alternatively or additionally, PTC material could be associated with the thick film heatin(-, element by mounting discrete PTC resistors to a printed circuit track provided for the purpose on the heating element.
Irrespective of ho,.v 'It is constituted, the PTC material should desirably be so associated with the thick film heating element that the PTC circuit has a common electrical connection terminal with the thick film heating element, since this would simplify the making of electrical connections to the thick film heatinu element, since only three connection terminals would be required, is though the PTC circuit could alternatively be formed with its own connection terminals, for enabline a low voltacye control supply to be used for example. Connection to the thick film heating element would preferably be made by employment of spring contact fingers adapted to contact terminal pads formed on the thick film heating element.
When the thick. filin heatin.--- element is In a cold condition or at a temperature within its normal operating range, the resistance of the PTC material is sufficiently low to permit the flow of sufficient current through the 3 the heatin,,. element varies as a function of its temperature. In EP-A-0 485 211 for example there is proposed an arrangement wherein the electrical resistance of a track formed on a thick film heatin. element is monitored electronically and remedial action taken if the resistance of the track changes by an excessive amount indicative of a heating element overtemperature condition. Yet another proposal made in GB-A-2 296 847 is to incorporate a PTC (positive temperature coefficient of resistance) material into a thick film heating element track so that the electric current throw,h the heatina element track is reduced as its resistance rises in response to overheating, and in GB-A-2 307 629 the W proposal is made to incorporate a PTC material into a thick film heating element track and to sense resistance changes electronically as in EP-A-0 485 211.
Obects and Sunirriary of the Invention..
It is the principal object of the present invention to provide an improved overtemperature protection stratagern for thick film heating elements C.1 by use of PTC materials.
According to the present invention, a thick film heating, element has associated therewith PTC material determining the current supply to the coil of an electromagnetic relay switch which in turn determines the current supply to the heatincy element.
The PTC material may be associated with the thick film heating element in a variety of different ways. It may consist of a single PTC 6 Description of the Drawings:
Figure 1 is a schematic circuit diagram of a first exemplary embodiment of the present invention., and Figure 2 is a schematic circuit diagram of a second exemplary embodiment of the present invention.
Detailed Description of the Embodimentsi
Referrina to Fioure 1, the schematic circuit diacram shown therein C) comprises a thick film heating element 1 connected to a relay 2 having a set of switch contacts 3 and a coil 4, and with a PTC resistance element 5 in series with the relay coil 4, a set Of 111,-111Lially-operable nori-nally-open switch contacts 6 paralleling the relay contacts 3 and a set of normally-closed switch contacts 7 in series with the parallel-connected contacts 3 and 6. In operation, the switch contacts 7 bein. closed, a momentary depression of the switch contacts 6 is sufficient to cause electric current to flow-throu(,h the relay coil 4 via the PTC resistance element 5. The relay thus operates to close the contacts 3 and the heating eiernent 1 is then po,ered, even after the switch contacts 6 are opened.
In the event of the thick film heatine, element 1 overheating, for C example because of a vessel havin- the heating element In its base being switched on without anv water in the vessel, the temperature of the PTC resistance element 5 rises and its resistance increases accordingly so that the current in the relay coil 4 is reduced to the point where the relay 2 drops out relay coil to allow the relay switch to operate so that the relay switch contacts supply current to the heating element. When the PTC material is exposed to an overtemperature condition, however, its resistance increases and the current in the relay coil decreases so that the relay opens its contacts thus switching off the heating, element.
Hereinafter described are two exemplary embodiments. In the first, the relay contacts are arranged to be momentarily shorted for initially energising the relay coil which causes the relay to switch and close its contacts, thereby ener-lzlna the thick film heatina element and ensurine a continuing flow of holdino, current through the relay coil until such tirne as the PTC material Z> increases its resistance on overheatin. of the heatincy element. In this first embodiment, the increase in resistance of the PTC material causes the relay to switch off the supply of electricity to the thick film heating, element and it will remain switched off until such time as the relay contacts are again shorted so as to ener(nze the relay coil. In the second embodiment, an ON/OFF switch determines the supply of electric current to the relay coil and the relay will cycle ON and OFF as the PTC material heats up, switches off the relay, and then cools down so that the relay again switches on.
The above and further features of the present 'invention are set forth with particularity in the appended claims and will be best understood, and their advantages appreciated, from consideration of the following detailed description given with reference to the accompanying drawings.
Z> 8 element 1 overheating by virtue of the appliance containing the element being switched on dry, the PTC resistance element 5 will increase its resistance, so causing the current in relay coil 4 to fall and causing relay contacts 3 to open, thereby disconnecting the heating element 1 from the power supply. The 11 then cycle, since with the heating element 1 switched offthe arranaement wi 1 1 1 - W PTC resistance element 5 will cool, the relay 2 will be operated again and the heatinc element 1 will again be powered. This cycling action could be prevented by arranging it that the heat generated by current flowing through the PTC resistance element 5 In its hi,),h resistance condition was sufficient to keep it in its h[(-,.h resistance condition.
The PTC resistance material is preferably selected to display a relatively sudden change of resistance above a predetermined temperature, its Curle point, so that the PTC resistance material acts almost as a switch to de-enemize the relay coil at a predetermined temperature. Ceramic materials such as Barium Titanate, exhibit a PTC effect with a sharp Curie point transition frorn low to resistance conditions. Glass materials Incorporating electrically conductive particles and which exhibit an appropriate resistance chan.e at the ---lasstransition temperature could possibly also be utilized, as could PTC thermoplastics polymers such as those loaded with electrically conductive carbon.
Having thus described the present invention by reference to specific embodli-nents, it Is to be appreciated that the ernbodiments are exemplary only 7 and the contacts 3 open thereby disconnectin-,-,,, the heating element 1 from its power supply. The heating element 1 cannot be switched on again until the PTC resistance element 5 has cooled, which can be effected by filling the aforementioned vessel with cold water.
The embodiment of Figure 1 is a form of manual reset dry boil control well suited to a push-button appliance having a first push-button switch 6 for momentarily bypassing the normally-open relay contacts 3 and a second push-button switch 7 for switching off the appliance by de-energizing the relay coil 4. The second embodiment, described hereinbelow, is adapted for use with an appliance having a steam switch for automatically switching off the appliance when water boils in the appliance and a dry boil control for switching off the heating element of the appliance in the event of the appliance being switched on without first being filled with water, the dry boil control being of a type adapted to cycle on and off until the appliance is subjected to manual is intervention.
Referrinu to FI,,ure 2, wherein the same reference numerals as were used in Figure 1 are used to refer to the same or similar parts, a thick film heatina element 1 is connected in circuit with relay 2 comprisincr contacts 3 and coil 4 and with PTC resistance element 5 and on/off switch 8. In operation, the switch 8 is operated into its "on" condition which causes current to flow in the relay coil 4, whereby the relay contacts 3 are closed so that the heating. element 1 is energized. In the event of a dry boil, namely the heating
Claims (1)
- CLAIMS:1 A thick film heating element having associated therewith a PTC material for determining the current supply to the coil of an electromagnetic relay switch.2. A thick film heatina element as claimed in claim 1 wherein the PTC material comprises one or more PTC resistance elements.1 1 3. A thick film heating element as claimed claim 1 or 2 wherein the PTC material comprises one or more tracks, or parts of tracks, formed on the thick film beating element.4. A thick film heatin-,- elernent as claimed in any of the preceding claims wherein terminal pads are provided for making connections to the heating element and to the PTC material bv means of spring contacts.5. A thick film heating element as claimed in any preceding claim wherein said PTC material is distributed about the periphery of the thick film heating element.9 and that modifications and variations thereto may occur to those possessed of relevant skills without departure frorn the spirit and scope of the present invention as set forth in the appended claims. For example, by limiting the PTC resistance element to a part of the thick film heating element which is not directly heated by the heating element track, lower temperatures will be possible and only a very small power dissipation will be required in the case of the Figure 2 ernbodirnent to hold the appliance off, the heat being localised in W the PTC track rather than in the main heating element track..P 11 6. A thick film heatina element as claimed in any preceding claim wherein said PTC material is located at a part of said heating element which is not directly heated by the heating elementeack or layer.7. A thick film heatinc,, element as claimed in any preceding claim wherein 1 - the PTC material has a relatively sharp Curie point transition from its low resistance to its high resistance conditions.8. A thick film heatim, element as clairned in any preceding claim wherein said PTC material comprises a loaded glass material exhibiting a relatively 0 - sharp Curie point at its glass transition temperature.0 9. A thick film heating element as claimed in any precedinc, claim in g combination with an electromagnetic relay.10. A thick film heating element and electromagnetic relay combination as claimed in claim 9 and wherein the arrangement is substantially as shown in Figure 1 or Flaure 2 of the accompanying drawings.11. An electronically heated water boiling vessel incorporating a thick film 0 1 1 1 heating element and electromagnetic relay combination as claimed in claim 9 or 10.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9807385A GB2336481B (en) | 1998-04-06 | 1998-04-06 | Improvements relating to control of electric heating elements |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9807385A GB2336481B (en) | 1998-04-06 | 1998-04-06 | Improvements relating to control of electric heating elements |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9807385D0 GB9807385D0 (en) | 1998-06-03 |
| GB2336481A true GB2336481A (en) | 1999-10-20 |
| GB2336481B GB2336481B (en) | 2002-10-16 |
Family
ID=10829955
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9807385A Expired - Fee Related GB2336481B (en) | 1998-04-06 | 1998-04-06 | Improvements relating to control of electric heating elements |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2336481B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000047095A1 (en) * | 1999-02-11 | 2000-08-17 | Otter Controls Limited | Improvements relating to control of electric heating elements |
| WO2002017456A2 (en) * | 2000-08-25 | 2002-02-28 | Tyco Electro Electronica Ltda. | Protective relay |
| DE10132514A1 (en) * | 2001-07-05 | 2003-01-23 | Diehl Ako Stiftung Gmbh & Co | Method for disconnecting the electrical supply to a heating element has a relay and temperature sensitive resistor in thermal contact |
| WO2005027577A1 (en) * | 2003-09-15 | 2005-03-24 | Gessler Electronic Gmbh | Thermal two point switch and method for switching off a heating resistor |
| GB2511040A (en) * | 2013-02-20 | 2014-08-27 | Frank Gough | Relay kettle |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3128090A1 (en) * | 1979-07-21 | 1982-04-22 | Limitor AG, 8022 Zürich | Thermal time switch |
| EP0485211A1 (en) * | 1990-11-09 | 1992-05-13 | Pifco Limited | Heating apparatus |
| GB2296847A (en) * | 1994-11-30 | 1996-07-10 | Strix Ltd | Plate type electrical heater with printed resistance track arranged to suppress localised overheating |
| GB2307629A (en) * | 1995-11-20 | 1997-05-28 | Strix Ltd | Thick film electric heater: Control of supply |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3740613A (en) * | 1972-04-12 | 1973-06-19 | Texas Instruments Inc | Apparatus for controlling the energization of a load |
| FR2671830B1 (en) * | 1991-01-17 | 1994-02-18 | Garrier Giraudeau Noel | ELECTRIC HEATER IN A PRESSURIZED ENCLOSURE WITH TEMPERATURE LIMITER. |
-
1998
- 1998-04-06 GB GB9807385A patent/GB2336481B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3128090A1 (en) * | 1979-07-21 | 1982-04-22 | Limitor AG, 8022 Zürich | Thermal time switch |
| EP0485211A1 (en) * | 1990-11-09 | 1992-05-13 | Pifco Limited | Heating apparatus |
| GB2296847A (en) * | 1994-11-30 | 1996-07-10 | Strix Ltd | Plate type electrical heater with printed resistance track arranged to suppress localised overheating |
| GB2307629A (en) * | 1995-11-20 | 1997-05-28 | Strix Ltd | Thick film electric heater: Control of supply |
Non-Patent Citations (1)
| Title |
|---|
| WPI Abstract Accession No 82-E7765E/17 & DE 3128090 A1 * |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000047095A1 (en) * | 1999-02-11 | 2000-08-17 | Otter Controls Limited | Improvements relating to control of electric heating elements |
| WO2002017456A2 (en) * | 2000-08-25 | 2002-02-28 | Tyco Electro Electronica Ltda. | Protective relay |
| WO2002017456A3 (en) * | 2000-08-25 | 2002-05-16 | Tyco Electro Electronica Ltda | Protective relay |
| US6657839B2 (en) | 2000-08-25 | 2003-12-02 | Tyco Electronics Corporation | Protective relay |
| KR100838022B1 (en) | 2000-08-25 | 2008-06-12 | 타이코 일렉트로 일렉트로니카 엘티디에이. | protective relay |
| DE10132514A1 (en) * | 2001-07-05 | 2003-01-23 | Diehl Ako Stiftung Gmbh & Co | Method for disconnecting the electrical supply to a heating element has a relay and temperature sensitive resistor in thermal contact |
| DE10132514C2 (en) * | 2001-07-05 | 2003-10-30 | Diehl Ako Stiftung Gmbh & Co | Safety circuit against overheating |
| WO2005027577A1 (en) * | 2003-09-15 | 2005-03-24 | Gessler Electronic Gmbh | Thermal two point switch and method for switching off a heating resistor |
| GB2511040A (en) * | 2013-02-20 | 2014-08-27 | Frank Gough | Relay kettle |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9807385D0 (en) | 1998-06-03 |
| GB2336481B (en) | 2002-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20120406 |